Polydipsia and Polyuria
neuronal irritation (pathologic thirst cause)
(hypothalamic) 1. tumor 2. trauma 3. inflammation
fluids
are complicated must add electrolytes otherwise diluting the body need extra by maintanance when replacing _________
pd and pu
both appear consistently in several polysystemic disorders. these diseases manifest in a disorder in water homeostasis
SG over 1.035
can concentrate their urine has to be something else
hypercalcemia (disorders causing pu)
cancer inhibition of ADH then mineralization of the kidney -> chronic renal failure
hypercalcemia (pathologic thirst cause)
cancer kidney dz lung tissue (mineral formation)
azotemic
cant get rid of toxins in the urine cause halitosis
renal disease (disorders causing pu)
decrease renal concentration mechanisms
Renin and Angiotensin
dipsenogenic compounds -compounds that stimulate thirst by direct action on neurons in thirst center -certain diseases cause an increase in ______ and/or ____________
Water Deprivation tests
dont do if animal is azotemic, dehydrated or hypercalcemic. used to R/o primary pd 1. 12 hour fast - blood serum osmolality, obtain SG evaluate 3-4 hours 2.terminate when concentrated urine is produced, weight loss of 7% or more occurs or there is increase in plasma protein/osmolality 3. failure to concentrate: -ADH deficiency -ADH unresponsiveness -Primary renal disease -medullary washout
polydipsia
excessive thirst persisting for long periods of time. Constant drinking abnormally excessive drinking
main treatment
fluids spiked 1st with dextrose -boost of energy -help them pee -if dont pee then kidneys shut down -start up the kidneys
Isosthenuric
glomerular filtrate with a specific gravity equal to plasma which is 1008 to 1012 urine is more concentrated than glomerular filtrate abnormality not as [ ] as should be -> renal problem
hyperadrenocorticism (disorders causing pu)
increased production of glucocorticoids ADH inhibition at the collecting ducts cushings-pendullus abd, bilateral allopeica, blackmarks, v, pu, pd, older animals
Iatrogenic
induced by humans usually drug induced
diabetes mellitus (disorders causing pu)
insulin deficiency -hyperglycemia -> glucosuria (profile) causing increased absorbable solute can test with dipstick
Antidiuretic hormone control center
lies adjacent to the thirst center this center is controlled by extracellular fluid osmolality
Countercurrent system (RCM)
loops of Henle water is reabsorbed along [ ] gradients established in the renal medulla -> this dec osmolality
medullary washout (disorders causing pu)
loss of countercurrent multiplier system chronic renal disease
diuretic
make urinate mannitol dextrose furosemide (lasix) osmotic diuresis
polyurias
many diseases produce ___________ by affecting renal concentrating mechanisms or by stimulating primary polydipsia
Pseudopsychogenic polydipsia (disorders causing pu)
not common primary polydipsia compensatory polyuria
secondary thirst (pd)
not well understood -anticipates water needs prior to actual deficiences -more common cause of Pd
2nd basic principle
overhydration vs. dehydration (intracellular)
Pathologic thirst
primary polydipsia (not compensatory) caused by: 1. neuronal irritation 2. compulsive water drinking 3. increased plasma renin 4. hypercalcemia 5.thoracic calval constriction
compulsive water drinking (pathologic thirst cause)
pseudopsychogenic polydipsia caused by: anxiety boredom compulsive, neurotic owners
brain trauma
put animal on diuretic to relieve pressure in the brain caused by fluid mannitol is small and can pass through the blood brain barrier furosemide is too large and cant get out of the system
polyuria & polydipsia disorders
several disorders produce pu and pd by disturbing distal and collecting tubular function
hydration status
tent the skin hematocrit PCV
polyuria
the passage of a large volume of urine in a given period. Usually urine has a decreased SG abnormally excessive urination
physical exam
thorough/complete weight, hydration status, CBC, profile, UA, plasma proteins specific gravity >1.005 is NOT pu measure water consumption
pyometra (disorders causing pu)
tubule unresponsive to ADH uterus full of pus
diabetes insipidus (disorders causing pu)
two types -neurogenic- neural injury causing def of ADH -nephrogenic- tubule enzyme def causing unresponsiveness to ADH loops of henle change permiability when bound - cant bind
1st basic principle
water in = water out acohol alcohol
primary thirst (pd)
well understood -intracellular dehydration -left atrial volume and pressure receptors - 8-10% decreases in blood volume induces thirst it is not a primary mechanism that determines water intake -> stimulates ADH/thirst center
ADH Vasopressin Response Test
when animals fail to [ ] urine obtain urine SG, withhold water and food, give SQ vasopressin tannate. Take urine SG at 30 min SG of >1.015 are normal failure to respond indicates primary renal disease, diabetes insip, or MW
kidney enzymes
BUN/ CREAT increased -usually indicate renal problem or enzyme in blood incidating some cell death -how can you tell how bad the problem is? ultrasound, rads, palp, UA, further tests, KIDNEY BIOPSY
diseases that cause pu by affecting RCM/stim 1st pd
1. diabetes insipidus 2. diabetes mellitus 3. hyperadrenocorticism 4. hypercalcemia 5. hyperthyroidism 6. liver failure 7. medullary washout 8. pyometra 9. pseudopsychogenic polydipsia 10. renal disease 11. iatrogenic
Diagnostic plan
1. document the problens of pu and pd exist - owners can mislead 2.Data base -> clues for diagnosis 3. perform urine concentration test 4. special diagnostic testing *also tissue sampling kidney tests/ exploratory surgeries *usually small animals have primary pu with compensatory pd
Urine Concentration test
1. water deprivation tests 2.ADH vasopressin Response test
Renal concentrating mechanism
25 lb dog -> 68 liters of fluid are filtered by the glomeruli each day but less than 500 ml is excreted as urine 1. ADH osmoreceptor control system 2. countercurrent system
ADH osmoreceptor control system (RCM)
ADH- produced by specialised neuorns stored in nerve endings - (hypothalamus-piticulocytes-nerve endings) inc extracellular fluid osmolality -> inc ADH release -> inc collecting tube permeability -> water to be reabsorbed
polydipsia, polyuria
______________ usualy results from primary _____________
thirst
a desire for water controlled in the hypothalamus/ stimulus to drink
iatrogenic (disorders causing pu)
alcohol causes inhibition of ADH release (dec nerve function) glucocorticoids - ADH inhibition - diuretic effect